iio: imu: st_lsm6dsx: add support to LSM6DSO16IS

Add support to STM LSM6DSO16IS (accelerometer and gyroscope) Mems sensor.

Datasheet: https://www.st.com/resource/en/datasheet/lsm6dso16is.pdf


Tested-by: Mario Tesi <mario.tesi@st.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/df6a9d4653cd69f7204190f8b6a9b618fd48bd23.1668605631.git.lorenzo@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>